The present application relates to a semiconductor structure and a method of forming the same. More particularly, the present application relates to semiconductor structures including a memory device in which a combination of a compressive metal-containing layer and a tensile metal-containing layer have been used to minimize wafer bow and litho overlay shift as well as a method of forming such semiconductor structures.
Memory device stacks which are used in fabricating a non-volatile random access memory device require bottom and top electrode layers composed of a thick conducting metal. Typically, transition metals with nitrogen are used as the conducting metal that provides the top electrode layer and the bottom electrode layer of the memory device stack. Tantalum nitride deposited by physical vapor deposition (PVD) often generates compressive stress which may cause buckling defects (i.e., wafer bowing) and litho overlay issues. Titanium nitride, which may provide a tensile stress, a compressive stress, or a neutral stress depending on the content of nitrogen in the titanium nitride itself, has a film morphology that is typically columnar when deposited by a PVD process. Columnar morphology for an electrode layer is not desirable since it provides a diffusion path source within the memory device.
There is thus a need for providing a memory device in which wafer bowing and litho overlay issues have been minimized.